Shock Wave Modification Method and System

ABSTRACT

A shock wave in a gas is modified by emitting energy to form an extended path in the gas; heating gas along the path to form a volume of heated gas expanding outwardly from the path; and directing a path. The volume of heated gas passes through the shock wave and modifies the shock wave. This eliminates or reduces a pressure difference between gas on opposite sides of the shock wave. Electromagnetic, microwaves and/or electric discharge can be used to heat the gas along the path. This application has uses in reducing the drag on a body passing through the gas, noise reduction, controlling amount of gas into a propulsion system, and steering a body through the gas. An apparatus is also disclosed.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/944,376, filed Jul. 17, 2013, which is further a continuation of U.S.application Ser. No. 13/397,088, filed Feb. 15, 2012, now U.S. Pat. No.8,511,612, which is a continuation of U.S. application Ser. No.11/540,964, filed Oct. 2, 2006, now U.S. Pat. No. 8,141,811, which isfurther a continuation of U.S. application Ser. No. 10/705,232, filedNov. 12, 2003, now U.S. Pat. No. 7,121,511, which is aContinuation-in-Part of application Ser. No. 10/342,347, filed on Jan.15, 2003, now U.S. Pat. No. 7,063,288, which is a Continuation-in-Partof application Ser. No. 09/867,752, filed on May 31, 2001, now U.S. Pat.No. 6,527,221, which claims the benefit of U.S. Provisional ApplicationNo. 60/208,068, filed on May 31, 2000. The foregoing relatedapplications, in their entirety, are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to facilitating the movement of objectsthrough a fluid and, more particularly, to modifying shock waves withinthe fluid.

BACKGROUND OF THE INVENTION

When a fluid is driven to flow at a relative speed, with respect to thefluid it encounters, that exceeds the speed of sound within theencountered fluid, one or more shock waves can develop. The driving ofthe fluid can occur when the fluid is pressed forward by an object orbody propagating through the fluid. Alternatively, the fluid can beaccelerated by a pressure gradient generated by any other means, such asin wind tunnels, propulsive units, jets, and rapid heating/expansion.When a shock wave is formed in a supersonic stream of a fluid, severalundesirable effects can occur.

If, for example, the supersonic stream of fluid results from apropulsive effluent stream, such as the discharge of a jet aircraft,then pressure jump(s) due to the difference in pressure across a shockwave can reduce the efficiency of the desired momentum transfer from thevehicle to the effluent stream. Additionally, a series of shock waveswithin the supersonic stream can augment the acoustic signature of thesupersonic stream in certain frequency ranges. This augmentation of theacoustic signature is undesirable for both environmental and detectionavoidance reasons. As a further example, if solid (or liquid) particlesin multi-phase supersonic flow are directed to propagate across a shockwave, such as during supersonic spray deposition, a potential problem isthat particles of different sizes and/or densities are affecteddifferently when they cross the shock wave. This can result in anundesired segregation of particles, or particle size redistribution atthe shock wave depending on the shock parameters and the size and/ordensities of the particles. Furthermore, when a body or vehicle isdriving a fluid forward, the driving body will typically feel the strongincrease in pressure across the shock wave as a drag force that impedesthe forward motion of the body. Another problem associated with theincrease in pressure across a shock wave is an increase in temperature.Again, if the shock is being driven by a body or vehicle, hightemperatures behind the shock wave can result in undesirable heating ofthe vehicle materials and/or components behind the shock wave. Thedeleterious effect of interacting shock waves and their hightemperatures and pressures can be yet stronger.

The control of shock waves by reducing the strength of the shock wave orcompletely eliminating the shock wave is sometimes referred to as flowcontrol. This term is used because the fluid flow is being controlled bymanipulating or affecting the shock wave(s) within the fluid. Whenconsidering vehicles/bodies, flow control also encompasses processeswhich reduce drag. This drag can be the overall or total drag, thereduction of which is intended to optimize the performance andefficiency of the vehicle. Alternatively, the drag reduction can bepreferentially applied to generate moments or torque, which is useful inmaneuvering the vehicle or maintaining certain angles of attack. Flowcontrol can also be used to reduce heating and modify acousticsignatures such as a sonic boom, which result directly from the shockwaves.

As a fluid element crosses from one side of the shock wave to the other,the fluid element experiences a sharp and theoretically discontinuousincrease in pressure. The magnitude of this increase or “pressure jump”is typically larger for stronger shock waves, which is characterized bya greater difference between the pressures on either side of the shockwave along a perpendicular line across the shock wave. As used herein,the term “reducing the strength” of a shock wave involves reducing thepressure difference across the shock wave along the original directionof flow by reducing or eliminating the pressure discontinuity within thefluid flow and/or diffusing or broadening the pressure jump to create ashallower pressure gradient across the shock wave in this originaldirection of flow. When a shock wave has been removed or eliminated, theformerly shocked flow becomes subsonic in the original direction offluid flow although, however, the flow may be supersonic or shocked indirections transverse (not limited to orthogonal) to the originaldirection of the fluid flow in the specific spatial region in question.

Reducing the strength of the shock wave, or eliminating it completely,can advantageously reduce or remove a sometimes significant portion ofthe drag force acting on the body due to the shock wave. This can bebeneficial to such bodies because a reduction in drag force increasesthe range and/or speed of the body. Therefore, the reduction in dragrequires less energy/fuel to propel the vehicle and/or allows for agreater payload of the vehicle or body for the same amount offuel/propellant required without invoking any drag reduction.

Another benefit of being able to reduce the strength of or eliminate theshock wave is the ability to steer the body or vehicle. If only certainportions of the shock wave are reduced in strength at a given time, suchas to one side of the body, then drag on the body can be preferentiallyand selectively controlled. Being able to control the drag on certainparts of the body allows the body to be steered by preferentiallycontrolling the strength of the associated shock wave(s) as well as theresulting pressure distribution along the body.

Since the first supersonic vehicle, there have been many developments toreduce the strength of shock waves; increase shock standoff distancefrom the vehicle; and reduce the stagnation pressure and temperature.One of the first developments was that of the aerospike 10, asillustrated in FIG. 1. This is typically a pointed protrusion extendingahead of the nose of the vehicle 12 or other critical shock-generatingsurfaces. The aerospike 10 effectively increases the “sharpness” of thevehicle 12, and is based on the idea of using a mechanical structure tophysically push air to seed transverse motion in the fluid, thusallowing the fluid to start moving laterally out of the way before thefluid actually encounters a larger part of the vehicle 12. Because theaerospike 10 pushes air, a shock wave 14 actually begins to develop whenthe ambient air encounters the tip of the aerospike 10.

Other developments, as illustrated in FIG. 2, have been the injection offluids 16, such as streams of water, gas, and heated and/or ionizedfluid, toward the shock wave 14 from the vehicle 12. These fluidextensions behave similarly to the aerospike and obtain similar effectsand benefits, because the counter-flowing fluid also pushes the ambientair forward and laterally before the air reaches a larger part of thevehicle 12. More recently, there have been attempts to ionize the airahead of a vehicle and its shock wave by using radio frequency (RF) ormicrowave radiation. Electromagnetic methods have the benefit that theycan pass through the gas without “pushing,” or imparting any momentum,to the gas. The electromagnetic radiation can therefore pass through ashock wave without significantly affecting it.

The microwave methods involve creating a spot ahead of the shock waveusing a microwave intensity high enough to heat and/or ionize the gas.One proposed method, as illustrated in FIG. 3A, is to focus a microwavebeam 26 emanating from the front of a supersonic vehicle 24 to a point28 ahead of the shock wave. Another proposed method using microwaves, asillustrated in FIG. 3B, has been to mount microwave horns 20 on thewings 22 on both sides of the vehicle fuselage 24. Each microwave horn20 emits a microwave beam 26 that is alone too weak to ionize the gas.However, when the two beams 26 are crossed in front of the vehicle 24,the combined electric field 28 is strong enough to ionize the gas. Bothof the aforementioned methods using microwaves disadvantageously must beoperated continually to maintain a hot and/or ionized path of gas aheadof the vehicle and/or shock wave. Furthermore, both of these methodsconcentrate on heating a single spot ahead of the shock wave; and assuch, much of the microwave energy is inefficiently used because of theresulting scattering.

Still another development has been the use of RF antennae 30 to generatea diffuse plasma near the body of the vehicle 12, as illustrated in FIG.4. This diffuse plasma 32 mainly affects the viscosity in the boundarylayer adjacent the vehicle 12 and heats a general area around thevehicle 12.

Electric discharges 34 have also been used to ionize the air around thevehicle 12, with a resulting heating geometry similar to that of the RFgenerated plasma, as illustrated in FIG. 5. In this method, an electrode36 of one polarity is positioned at the tip of the vehicle 12, andseveral oppositely polarized electrodes 36 are positioned along the bodyof the vehicle 12 further downstream. When the discharge 34 isenergized, the discharge 34 results in a diffuse heating/ionizationaround the vehicle body 12, between the oppositely polarized electrodes36, which tends to modify the shock wave 14.

The problem of flow control at high speeds is becoming more important asthe demands on both speed and maneuverability in flight systems areincreasing. As previously discussed, one approach to flow controlinvolves mechanical manipulation of the air stream around the vehiclebehind the shock wave. However, an attempt to extend an object ahead ofthe shock wave typically creates a shock wave of its own.

Some methods of mechanical flow control behind the shock wave use theairframe and control surfaces to divert the flow or employ impulsivelateral thrusters. However, as the speed increases to higher Machnumbers, using control surfaces to steer the body requires increasinglygreater power to offset the higher pressures encountered at thesespeeds. These power demands typically cannot be met by the controlsystems designed for subsonic flow and low supersonic Mach numbers.

The increasing demands and limitations on conventional control systemshave led to the desire to develop new concepts for actuators and flowcontrol systems. It is further desired to reduce or eliminate the needfor moving parts and also to work with the high speed gas flow, insteadof fighting against it. It is, therefore, desirable to develop a newfamily of control systems whose performance is optimized at extremelyhigh speeds. For craft that may operate at both subsonic and supersonicspeeds, these systems will complement the current methods of flowcontrol, which are very effective at low speeds but increasinglyimpracticable at higher speeds. There is, therefore, a need for a devicewith a minimal number of moving parts, and whose effectiveness increaseswith increasing Mach number.

Additionally, there is a need for an improved method of modifying shockwaves to reduce or eliminate the pressure discontinuity within the fluidflow. Such a modification to the shock wave can eliminate or reduceassociated problems with momentum transfer efficiency, particulatetransfer efficiency, and/or acoustic signature. Furthermore, themodification of the shock wave can reduce heating that results from theshock wave, thereby reducing the need for complex cooling methods,reducing cost, and further expanding the performance envelope of thevehicle associated with the shock wave.

Besides increased drag, sonic boom, and destructively high temperaturesand pressures on their airframe and components, the shock waves producedby hypersonic and supersonic vehicles/missiles produce additionaltechnical challenges. For example, deploying munitions from supersonicvehicles produces further complications, as the multiple bodies andshock waves interact with each other. The problems attendant with suchcomplications are traditionally circumvented by reducing the vehicle'sspeed to subsonic before deployment. However, reducing the vehicle'sspeed to subsonic adds new elements of risk and negates the benefits oftraveling at hypersonic/supersonic speeds. Therefore, there is a needfor an improved method and delivery system capable of safely andreliably deploying objects, such as munitions, while maintainingsupersonic cruise conditions. Furthermore, there is a need for a systemthat can be retroactively applied to existing air platforms. In therealm of subsonic and transonic flight there is also room forimprovement in the areas of drag reduction and flow control.

SUMMARY OF THE INVENTION

These and other needs are met by embodiments of the present inventionwhich provide a system for modifying a shock wave in a gas by emittingenergy to form an extended path in the gas; heating gas along the pathto form a volume of heated gas expanding outwardly from the path; anddirecting a path. The volume of heated gas passes through the shock waveand modifies the shock wave. This eliminates or reduces a pressuredifference between gas on opposite sides of the shock wave.Electromagnetic-, microwave- and/or electric-discharge can be used toheat the gas along the path. This application has uses in reducing thedrag on a body passing through the gas, noise reduction, controllingamount of gas into a propulsion system, and steering a body through thegas. The method and apparatus can also be applied to subsonic andtransonic flow.

Additional advantages of the present invention will become readilyapparent to those skilled in this art from the following detaileddescription, wherein only an exemplary embodiment of the presentinvention is shown and described, simply by way of illustration of thebest mode contemplated for carrying out the present invention. As willbe realized, the present invention is capable of other and differentembodiments, and its several details are capable of modifications invarious obvious respects, all without departing from the invention.Accordingly, the drawings and description are to be regarded asillustrative in nature, and not as restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference is made to the attached drawings, wherein elements having thesame reference numeral designations represent like elements throughoutand wherein:

FIG. 1 is a partial side view of an aerospike in accordance with theprior art;

FIG. 2 is a partial side view of a method of expelling heated fluidahead of a supersonic aircraft in accordance with the prior art;

FIGS. 3A and 3B are top plan views of methods of using microwave energyto heat a specific location ahead of a supersonic vehicle in accordancewith the prior art;

FIG. 4 is a partial side view of RF antennae on a vehicle to generate adiffuse plasma near the vehicle in accordance with the prior art;

FIG. 5 is a partial side view of oppositely polarized electrodes on avehicle in accordance with the prior art;

FIG. 6 is a partial top plan view of a shock wave adjacent to a body andstreamlines flowing into the shock wave;

FIG. 7 illustrates a heated core being formed through the shock wave ofFIG. 6 in accordance with the present invention;

FIG. 8 illustrates the heated core of FIG. 7 expanding and puncturingthe shock wave;

FIG. 9 illustrates a heated core being formed asymmetrically through theshock wave of FIG. 6 so as to form asymmetrical forces against the body;

FIG. 10 illustrates a heated core being formed asymmetrically throughthe shock wave of FIG. 6 so as to form asymmetrical forces against thebody;

FIGS. 11A-11D is a partial top plan view of a shock wave in front of abody being punctured in accordance with the present invention;

FIG. 12 is a partial side plan view of a body passing through a fluidwith a non-zero angle of attack in accordance with the presentinvention;

FIG. 13 is a partial top plan view of a body using a set ofelectromagnetic and electric discharge emitters in accordance with thepresent invention;

FIG. 14 is a schematic view of electromagnetic and electric dischargeemitters similar to those in FIG. 13;

FIG. 15 is an enlarged schematic view of an emission port shown in FIG.14;

FIGS. 16A and 16B are partial plan views of a body using an array ofenergy discharge devices in accordance with the present invention;

FIG. 17 is a partial cross-sectional view of a propulsion unit usingenergy discharge devices in accordance with the present invention;

FIG. 18 is a partial cross-sectional view of a supersonic spraydeposition unit using an energy discharge device in accordance with thepresent invention;

FIG. 19 is a partial top plan view of a propulsion unit using an energydischarge devices to modify the acoustic signature of the propulsionunit in accordance with the present invention;

FIG. 20 is a partial top plan view of a wing on an aircraft using alinear array of energy discharge devices in accordance with the presentinvention;

FIGS. 21A and 21B are plan views of a submersible body using energydischarge devices in accordance with the present invention;

FIG. 22 is a plan view of a heated core being generated adjacent to abody from an energy discharge device located away from the body inaccordance with the present invention;

FIG. 23 is a side view of a protrusion on a body using an energydischarge device in accordance with the present invention;

FIG. 24 is a cross-section view of a propulsion unit using energydischarge devices in accordance with the present invention;

FIGS. 25A-25E illustrate several examples of the different geometries inwhich energy discharge devices can be arranged on a body in accordancewith the present invention;

FIG. 26 is a side view of an energy discharge device located away from alight craft being used to direct energy ahead of the craft in accordancewith the present invention;

FIGS. 27A-C illustrate examples of modifying an amount of air reaching asymmetrical inlet(s) of a projectile in accordance with the presentinvention;

FIG. 28 illustrates a projectile having a non-symmetrical inlet(s) inaccordance with the present invention;

FIG. 29 is a chart graph illustrating drag for Mach 2 flow over a 450half-angle cone at Mach 2 in accordance with the present invention; and

FIGS. 30a-f are plots of Maximum Drag Reduction (FIGS. 30 a, c, e) andEnergy Efficiency (FIGS. 30 b, d, f) for cone half-angles at 45°, 30°and 15°.

DETAILED DESCRIPTION OF THE INVENTION

The present invention involves heating an extended path of fluid along astreamline ahead of a shock wave. A single energetic pulse can be usedto heat a core of fluid, and this heated core continues torelieve/reduce the strength of the shock wave with no further energyinput as the heated region of fluid streams into the initially shockedregion. Alternatively, the shock may be moving into the hot/expandingfluid. The energy can be deposited, for example, by high-powerelectromagnetic radiation pulses or by electric discharges along anionized path of an electromagnetic radiation pulse through the fluid.The additional energy deposition of the electric discharge allows theinvention to affect a larger area, which can be useful inmodifying/controlling larger diameter shock waves. The invention canalso be used to modify the shock wave in such a manner as to maneuver abody through a fluid. The invention provides the ability to depositelectromagnetic energy in the form of heat and ionization along verylong paths of gas/fluid.

As illustrated in FIG. 6, the method and apparatus of the invention,referring to a modification, such as elimination or reduction of thestrength, of a shock wave 54 in a fluid 56, and/or control of the shockwave 54, will be described in the reference frame of the unmodifiedshock wave 54. In this reference frame, the shock wave 54 is stationary,and the medium or fluid 56 with parameters of a given density, pressure,and temperature distribution flows into the shock wave 54 from one sideof the shock wave 54. As the fluid 56 crosses the shock wave 54, thefluid 56 typically experiences an increase in these parameters, themagnitude of which depends on the Mach number of the flow. Thetrajectories followed by “fluid elements” as they flow into the shockwave are typically called streamlines 58. Although the shock waves 54are intended to be modified/reduced as a result of the invention, theshock wave 54 is shown in an unaltered state for purposes of describingthe invention. If the unmodified shock wave created by a body/vehicle isstationary, the shock dynamics can also be described in the rest frameof the vehicle's average motion.

It should be noted that the methods, apparatus, and systems of thepresent invention are applicable to any body 50 and any fluid 56 in anyrelationship to each other where a shock wave 54 forms in the fluid 56and affects the fluid near the body 50. They are also applicable in anyfluid-flow, in which a shock wave 54 is present. Furthermore, in densefluids, such as liquids, the methods, apparatus, and systems can bebeneficially applied even in the absence of shock waves. The methods,apparatus, and systems of the present invention are also applicable toany body 50 and any fluid 56 in which a shock wave 54 is not present. Insuch a situation, subsonic and/or transonic flight for example, thebenefit of the present invention can still be expected, albeit possiblyto a lesser degree than such a situation as supersonic flight. Forexample, the method and apparatus of the present invention can be usedto reduce drag of the body 50 moving sub sonically or transonicallyrelative to the fluid 56 by creating a path of lower density fluid 56 infront of the body 50.

Potential driving bodies 50, which create the shock wave includevehicles, such as airplanes, submarines, torpedoes, missiles, killvehicles, launch vehicles, unmanned vehicles, supersonic/hypersonictransports, delivery vehicles, entry vehicles, and re-entry vehicles;portions of vehicles, such as protrusions, accessories, rotor blades andpropeller blades; projectiles; and portions of projectiles, such asmissiles, bullets, warheads, and meteoroids. Again, when travelingthrough a dense fluid such as a liquid, this technology can beadvantageously applied, even in the absence of shock waves at subsonicspeeds. The fluids 54 through which these bodies 50 pass include ionizedand non-ionized gases, such as air, and its components, methane andnoble gases; liquids, such as water; and mixtures of the gases andliquids, and/or other fluids such as multi-phase fluids, such as dustygases and aerosols. Additionally, the fluids may be those encountered innon-terrestrial atmospheres. Other flows can include fluids flowingthrough propulsive systems, such as air, air/fuel mixtures, reactiveflow; reaction products passing through and/or out of combustionengines; and ionized or charged flow passing through electromagneticallydriven propulsion systems. Such flow can also take place in other flowpaths such as a nozzle or duct, or even in a supersonic jet stream,defined and delineated solely by its velocity gradients.

The method of modifying and/or controlling a shock wave 54 involvesheating the incoming fluid 56 along a given streamline 58. Asillustrated in FIGS. 7 and 8, in one aspect, a heated core of the fluidflows into the shock wave 54 through a particular location P in theunmodified shock wave reference frame. This process is discussed interms of a steady shock wave, although the dynamic nature of the shockwave 54 implies that the shock wave 54 may be changing throughout theprocess, to which the present invention applies as well. Although, asdescribed, the incoming streamlines 58 are approximately straight lines,the present invention is not limited in this manner, and the inventionapplies to streamlines that are not constant due to the evolvingdynamics or are not straight lines. As the path is typically heated byelectromagnetic radiation, the path is also typically effectively astraight line, and the heated path advantageously coincides with thestraight streamline 58. Upon heating a fluid path ahead of the shockwave 54, an effectively cylindrical shock wave may propagatesubstantially outward from this path. This cylindrical shock wave willweaken as it expands, but regardless of the evolution of the cylindricalshock wave, the long heated region resulting from the different heatingmethods may also be referred to herein as a “low-density”/“heated”“core”/“filament” 60 at various stages of its evolution.

As illustrated in FIG. 8, the shock wave 54 can respond to the heatedcore in that the shock wave 54 is removed locally, such that fluid flowis no longer supersonic in that location because the speed of sound issufficiently high in the heated core. Alternatively, the strength of theshock wave is reduced as the heated core flows into the shock wave, suchthat the fluid flow is still supersonic (not shown), although with alower local Mach number.

One advantage of the present invention is that the pressure behind theshock wave is reduced locally where the shock wave meets the heatedcore, and this reduction in pressure occurs because the heated core actsas a channel for the escape of high-pressure gas trapped behind theshock wave. A shock wave typically forms because ambient fluid is beingpushed faster than the ambient fluid's speed of sound, such that thefluid is being pushed faster than a pressure buildup can “radiate away”via sound waves. When a streamline of fluid ahead of the shock wave isheated in accordance with the present invention, the heated core becomesa channel having a lower density and a higher speed of sound than thenon-heated fluid. If the temperature of the heated fluid is sufficientlyhigh, the speed of sound within the channel can be faster than thevelocity of the shock through the ambient fluid. When this occurs, thehigh-pressure fluid, formerly contained behind the shock wave can flowforward along the heated core, thus releasing some pressure.

The heated core forming a channel through the shock wave is analogous toa “puncturing” of the shock wave. Once the shock wave is punctured, theformerly sharp increase in pressure across the shock wave fades to ashallow pressure gradient, which drives the forward flow of heatedfluid. Even if the speed of the fluid remains supersonic within theheated channel, the standoff distance increases between the body and itsshock wave. Although the shock wave is not fully eliminated, thisincreased standoff distance and weaker shock wave are commensurate witha locally reduced pressure on the body behind the shock wave.

An additional advantage of this process, as compared to previousprocesses in which heated fluid was expelled in front of a body, is thatprevious processes have to overcome the mechanical resistance of thefluid in front of the vehicle that resists the movement of the expelledheated fluid. This is particularly a concern as the speed of the bodythrough the fluid increases. However, the present invention does notexperience this problem as the energy source to heat the fluid is notconstrained by any mechanical resistance.

Given an oblique shock wave, such as with the conical bow shock of asupersonic vehicle, additional benefits can be obtained when fluid ispropagating substantially laterally outward from the heated core aheadof the shock wave. When a streamline along the stagnation line isheated, the geometry of the heated core is particularly effective atseeding lateral motion away from the body that is generating the shockwave to be modified/weakened. The outward motion from the heated coreprecipitates more effective lateral escape of the ambient fluid when theexpanding fluid core crosses the body's shock wave. Otherwise, the fluidalong the stagnation line unexpectedly encounters the shock wave andstagnates temporarily in unstable lateral equilibrium. As thelow-density heated core is created directly in front of the stagnationpoint, less fluid impinges on this point, and this results in a lowerstagnation pressure and a lower stagnation temperature at that point.Additionally, the more the fluid is heated, the stronger the lateralflow is away from the heated core.

In some aspects, the creation of the heated core can be strong enough tocreate laterally-moving shock waves. These laterally-moving shock wavescan be very effective at laterally “sweeping” the fluid from in thefront of the shock wave. In the case of a liquid, strongly heating aswath of fluid along a streamline in front of a shock wave can vaporizethe liquid to a gas, and this results in a large reduction in densityalong the heated core. Similarly, this heating drives a strong lateralmovement of dense fluid away from the heated/vaporized core, and thehot, vaporized core allows for the body to more easily pass through thearea previously occupied by the dense fluid. As liquids are generallymuch more dense than their corresponding gases, this method isparticularly useful for reducing drag in liquids, even at sub-sonicspeeds when there is no shock wave present.

To more effectively modify the shock wave, the heated core is formedsuch that as much of the heated path as possible is along a streamlinecoming in toward the shock, as considered in the reference frame of theshock wave. Furthermore, a stronger and quicker heating of the fluid istypically better, because this increases the size of the heated core.Also, the fluid in the heated core is yet less dense and expands outwardyet faster. If the fluid is heated strongly and quickly enough, alaterally-propagating shock wave away from the heated core can beformed.

The invention is not limited as to the manner in which the heated coreis created. For example, the heated core can be formed usingelectromagnetic radiation, such as from WV laser pulses, visible laserpulses, IR laser pulses, and/or combinations thereof. In one example,the electromagnetic radiation is provided through the use of afilamenting laser. Alternatively, the heated core can be formed using anelectric discharge. The use of an electric discharge can be much moreeffective at heating a fluid than electromagnetic radiation, such asfilamenting lasers. For example, the heating provided by electricdischarge is less expensive than comparable heating provided by afilamenting laser. However, the exact path the electrical dischargetakes is typically difficult to control. This presents a potentialproblem in situations in which a precise geometry of the path of theheated core is desired. In contrast, the path of the filamenting lasersis very controllable because the heated core is generated in the path ofthe laser pulse. The beginning and end of the strongly heated region canalso be controlled by adjusting how the pulse is focused, in addition toother parameters described in more detail below. In some cases, however,electromagnetic radiation alone may not be able to produce asufficiently heated core to provide an effective control/modification ofthe shock wave.

In one aspect of the invention, the energy source is pulsed. In sodoing, energy savings can advantageously be realized. During theformation of the heated core with a single pulse, a long volume of fluidcan be heated, and in certain instances a substantially cylindricalshock wave is propagated outward from the heated core. Additionally, asthe heated core flows into the vehicle's shock wave, the heated corerelieves the pressure behind this shock wave. Eventually, the shock waveredevelops; however, until the shock wave redevelops, the pulsed energysource has provided a period of benefit by modifying the shock wave.When the shock wave redevelops or before the redevelopment of the shockwave, the energy source can again be pulsed to provide the samebenefits. In this manner, the energy source is not being continuallyused to obtain the benefits of modifying the shock wave. Instead, theenergy source is used intermittently and can be timed to operate whenheating provided by the energy source(s) produces the most dramaticand/or efficient beneficial effects. The pulse repetition rate of theenergy source and the length of the resulting heated cores are notlimited to a particular range and can be adjusted according to variousfactors, such as the density of the ambient fluid and the velocity ofthe fluid/shock wave.

Operating in this pulsed mode can produce results nearly as good asthose for continuous heating, in fact, there are even additionalbenefits which come from the violent expansion outward from the suddenlyheated path. Furthermore, much less energy is expended in the pulsedmode, than for comparable results obtained through continuous, or anyother kind of heating in a less extended region.

Alternatively, the energy source can be continually discharged to formthe heated core. For example, the continual output of an electricdischarge can provide a greater overall effect on the shock wave andprovide for greater drag reduction. As previously discussed, however,the continual discharge of the energy source has the disadvantage ofrequiring a greater energy usage and also is very difficult to guide andcontrol.

More than just one type of energy source can be used to create theheated core. For example, electric discharge can be used in conjunctionwith electromagnetic radiation to create the heated core. In thisexample, the electric discharge is initiated and guided by the ionizedpath resulting from the electromagnetic energy deposited in the fluid.In operation, the electromagnetic energy, such as a filamenting laser,ionizes and heats the fluid in a substantially straight path through thefluid. The ionized fluid is more conductive than the fluid around it;and therefore, the electric discharge follows the ionized path tofurther heat the ionized core through ohmic heating. In addition tobeing conductive to an electric discharge, the ionized fluid also isvery absorbent to microwave energy. Thus, microwave energy can be usedin addition to, or in place of, the electric discharge to create theheated core.

One approach to forming the ionized path through the fluid for use bythe electric discharge and/or microwaves is with an ionizingelectric-discharge/microwave guidance system. An ionizingelectromagnetic radiation/microwave guidance system, whether filamentingor not, defines an unambiguous path along which the electric dischargecan deposit its energy, after escaping from a highly charged electrodeor along which microwaves can deposit their energy, through absorptionby the ionized region. The filamenting laser, however, results in muchstronger, more effective, and more controllable ionization and energydeposition.

With the use of only one highly charged electrode, for example, at thetip of a vehicle, if an electric discharge escapes, the electricdischarge will do so in a substantially uncontrolled direction along anerratic path. If an oppositely polarized second electrode is situatedclosely enough to the first electrode, the high voltage will dischargebetween these two electrodes, and again, typically with an erratic path.However, with the use of the ionizing electromagnetic radiation system,the electric discharge can be sufficiently “straightened out” to directthe electric discharge to heat streamlines coming in toward a shock waveas described above. One such ionizing electric discharge guidance systeminvolves the use of filamenting lasers. When coupled with strongelectric discharges, the filamenting laser can also be used to modifythe shock wave on a smaller scale than that of using electric dischargealone. This additional flexibility allows for finer flow control. Thesame effect can also be achieved when microwaves are used in place of,or in addition to, the electric discharge.

Typically, when electromagnetic energy/radiation is focused to a pointto ionize a fluid, the resulting plasma disperses the beam. However,high-power pico- and femto-second-duration laser pulses have been foundto propagate over large distances, while heating/ionizing the fluid intheir path and this effect has been extrapolated over yet greaterdistances for UV laser pulses exceeding nanoseconds in pulse duration.This phenomenon is sometimes referred to as filamentation, andfilamentation has been observed using a variety of gases, such asnitrogen, helium, and air. Filamentation has also been demonstrated inliquids and solids, although with shorter propagation lengths. Thewavelengths for filamentation have been observed ranging from infraredto ultraviolet, although a greater range of wavelengths is possible. Theobserved pulse durations for filamenting lasers have been reported tovary from picoseconds to tens of femtoseconds, with UV filamentsprojected to exist using nano-second pulses and longer, leaving behindionized paths kilometers in length. Additionally, filamentation has beenobserved with a variety of laser pulse frequency modulation or “chirp”profiles. The pulse energy needed to initiate filamentation has alsobeen observed to range from milliJoules to Joules.

With these filamenting lasers, creation of the long, hot filaments isgenerally easier when using shorter wavelengths. For example ultravioletwavelengths ionize better than infrared wavelengths. The filamentationalso typically depends on intensity-dependent “self-focusing”coefficient(s), often necessitating high intensities, especially forpropagation through very low-density materials/fluids such as gases.High intensities can be achieved with high energy, short durationpulses, and for shorter wavelengths or greater photon energies, theintensity requirements are typically lower. This technology has beeninvestigated most intensively for optical and near-optical frequencies;however, the filamentation is broadly applicable over most of theelectromagnetic spectrum, and therefore not restricted to any particularset of wavelengths or frequencies.

With regard to spatial qualities, filamenting pulses have been reportedto travel as far as 12 kilometers, although a more reliable value ishundreds of meters, while the filament diameters have been reported torange from 0.1 millimeter to several millimeters. As known by thoseskilled in the art, the laser pulse can be focused and adjusted tocontrol both the point at which filamentation begins and the length ofthe filament through the fluid in which the laser pulse propagates. Theparameter ranges listed above are exemplary only and are continuallybeing expanded. Additionally, the invention is not limited as to theparticular devices used to form the filamenting pulses.

The greatest extent to which heating systems applied in the prior artcan expect to significantly deposit heat using a conventional focusedbeam of coherent electromagnetic radiation is about twice the Rayleighrange, centered about the beam waist. In contrast, filamenting laserpulses can significantly heat/ionize extended paths of fluid overhundreds of meters. For the systems which create these pulses, this isseveral orders of magnitude beyond the limitations experienced bysystems utilized in the prior art. It should be noted that differentpulse parameters and modulations (chirps) result in different beginningpoints and lengths of the filaments.

The invention is not limited as to the direction relative to the shockwave from which the energy emanates to create the heated core of fluid.For example, in certain embodiments of the invention, which will bediscussed in more detail later, the energy source, such as a filamentinglaser pulse, emanates from in front of the shock wave. In otherembodiments, however, the pulse emanates from behind the shock wave.Either orientation of the energy source relative to the shock wave cangenerate substantially identical heated cores, and as such, the fluiddynamics and flow control resulting from the heated cores aresubstantially the same. The non-restrictive nature of the location ofthe energy source relative to the shock wave provides, for example,flexibility in spray deposition applications, in which both sides of theshock wave are typically accessible. As another example, when a heatedcore is created using both a filamenting laser and an electricdischarge, which is discussed in more detail below, the vehicle can beequipped with the capacity to generate the electric discharge, and thefilamenting laser that is used to guide the electric discharge can belocated remotely and directed toward the moving body associated with theshock wave to be controlled. Additionally, as discussed above,microwaves can be used in place of, or in addition to, the electricdischarge to create the heated core of fluid.

The invention is not limited as to the length of the heated core, aslong as the heated core is capable of modifying the shock wave. Forexample, in certain aspects of the invention, the length of the heatedcore can range from about 0.01 meters to 100 meters in length. Inanother aspect of the invention, for example with use in overall dragreduction, the length of the heated core is about 0.1 to about 2.0multiplied by the product of M and d (M×d), wherein M is the Mach numberof the body and d is the diameter of the body or feature that iscreating the shock wave. Furthermore, the invention is also not limitedas to the repetition rate at which the heated core is created. In oneaspect of the invention, however, the repetition rate is about 0.5 toabout 10.0 multiplied by (c/d), wherein c is the ambient speed of sound.For more targeted flow control applications than general drag reduction,the heated path length can be significantly smaller with much higherrepetition rates than listed above. In another aspect of the invention,the length of the heated core is between about 1.0(M×d) and about100(M×d) with a repetition rate of between about 0.01(c/d) and about1.0(c/d). In yet another aspect of the invention, the length of theheated core is between about 2.0(M×d) and about 1000(M×d) with arepetition rate of between about 0.001(c/d) and about 0.5(c/d).

The invention can be used to reduce the stagnation temperature and dragon one or more strategic points of the airframe of the body, as well aspossibly reduce the total drag of the body in an economical fashion.Furthermore, the invention can be used to guide or steer the body bypreferentially controlling the flow and pressure distribution around thebody by directing pulses asymmetrically. For example, the path of thepulses relative to the shock wave can be actively changed to change themanner in which the shock wave is modified over time.

As described earlier, creating a heated core along the stagnation lineof a body's bow-shock wave will typically result in the greatest overalldrag reduction. As illustrated in FIGS. 9 and 10, when a heated core 60is generated preferentially on a given side of the stagnation line ofthe body's 50 bow-shock 54, the preferentially reduced drag will resultin the capability of maneuvering the body 50, instead of or in additionto only reducing drag. This concept applies whether or not the body 50is symmetric, although different degrees of symmetry may contribute tomore or less resulting torque/moment/rotation of the body about a givenaxis.

The invention has application in flight systems that may operate in asubsonic or transonic regime, or in whole or in part, in a supersonicregime. There is a current emphasis on increasing speed in flight andweapons systems, and control and maneuverability are of vital concern.One application of the present invention is to eliminate the need forproblematic cooling methods, necessary on certain vehicles, by reducingthe stagnation temperature in front of domes/fairings, which may also betransparent in certain frequency ranges of electromagnetic radiation.

Hypersonic craft are currently limited by issues of propulsion,materials, and flow control. One advantageous aspect of the dynamicsdescribed here is that the benefits generated by the present inventionincrease with higher Mach numbers. As the pressure behind the shock wavebecomes greater, as a result of a higher Mach number, the relativepressure reduction by the present invention increases. Therefore,greater benefits can be realized with stronger shock waves given asufficiently heated core to puncture the shock wave.

Additionally, the minimization of moving parts also reduces the risk ofactuator failure. One application of the invention is flow controlduring supersonic/hypersonic flight for maneuvering, drag reduction, andthe control of shocks near and within supersonic inlets, exhausts, andpropulsive units. Even in the situation of supersonic/hypersonic flight,where the bow-shock is attached to the vehicle and the stagnation pointis ahead of the point at which the shock attaches to the body, creationof a low-density core along the stagnation line will provide greatrelief from the extremely high temperatures and pressures at thestagnation point as well as overall drag reduction.

In the case where a filamenting laser is used to nucleate and guide anelectric discharge, precise positioning and control of the ionizedfilament can promote better electrical connections. Density fluctuationsencountered in a medium during the formation phase of the filament, asthe radiation pulse focuses to tighter spatial confinement, can be asignificant source of error in the formation process. To obtain bettercontrol this formation process, the formation process can take place ina controlled atmosphere, consisting of gas pressures, temperatures, anddensities, including but not limited to vacuum and any number of gasesor mixtures of gases. To separate this controlled atmosphere from theexternal atmosphere and flow environment, through which the filamentwill ultimately propagate, an aerodynamic window can be implemented.

An aerodynamic window can separate two distinct cavities, each at itsown distinct pressure, with a stream of gas. This stream of gas can varyin composition, and can expand through a nozzle from high pressure tolow pressure. This expansion can produce a pressure gradient, which isoriented roughly transverse to the flow and which is precisely tailoredto match the two external pressures which are to be separated by theflow. A hole exists in either side of the section containing the flow,through which the radiation can propagate. The physical holes aregenerally necessary, since any solid or liquid window would be destroyedby the high intensities of the radiation pulse or filament, and would inturn damage the filament formation process. However, because of theeffectively matched pressures at either side of each hole, theradiation/filament can pass through them, while gas flow issignificantly reduced either-into or out of the controlled focusingchamber or across the hole leading to the external environment. Theaerodynamic window allows the use of a controlled environment, in whicha laser/radiation pulse can focus to create a filament, without havingthe problem of gas flowing into or out of the exit hole of thecontrolled chamber. The density fluctuations which would result fromsuch flow would limit the desired controlled formation. The radiationcan be focused such that it would have the desired beam size at a pointin a self-focusing medium, such as the gas in the aerodynamic window orexternal environment, to allow for the desired filament formation.

A representative drag curve during the interaction of a cone with aheated core is shown in FIG. 29. To more quantify a benefit provided bythe described drag-reduction technique, a Weighted EssentiallyNon-Oscillatory (WENO) numerical implementation of the Euler equationswas used to model the gas flow. A cone at zero angle of attack wasplaced in flows of Mach 2, 4, 6, and 8, with cone half-angles of 45°,30° and 15°. The pressure over the entire cone surface was integrated toestimate the drag on the cone, and a path five times the length of thecone was suddenly heated along the cone's stagnation line. This path washeated in a manner such that the resulting low-density core was fullyopened when it reached the cone. Cores were opened up to radii equal to¼ R, ½ R, ¾ R, and the full radius R of the cone base. The cone base waskept constant for all of the simulations, which resulted in the smallerhalf-angle cones being longer. Since the heated cores were five timesthe length of the cone, longer cores were created for smaller half-anglecones. As illustrated in FIG. 29, the drag is seen to momentarilyincrease when the outward moving shockwave of the core is encountered.However, the drag drops dramatically once the low-density region isentered, and the drag reduction persists, until after the core hasstreamed past the cone, which is after the cone has fully traversed thecore.

The energy required for the cone to propagate through the air perturbedby the heating/core was compared to the energy required to propagatethrough the same length of undisturbed air. This comparison wasintegrated over the period of time, during which the perturbed dragdeviated significantly from the unperturbed steady-state value. The“return” on this invested energy (i.e. the energy efficiency) was thendetermined by subtracting [the energy required to create the core] from[the energy saved in flight], divided by [the total amount of energyrequired to create the core].

FIG. 30 shows a return of up to 65 times the invested energy for thesimulations performed. Put differently, for each Joule or Watt expendedahead of the cone, 65 fewer Joules or Watts can be expended in thrust tomaintain the cone's velocity. The energy efficiency depends strongly onthe Mach number, the radius of the core, and the cone angle. Additionalbenefit may be experienced by generating longer cores. The Eulerequations were used for the simulations since they capture the dynamicsof the shock waves and the associated “wave drag.” Additionalinformation can be acquired by including viscous terms in thesimulation. These terms are anticipated to provide further benefitsbecause of the reduced “viscous drag” that will accompany thehigher-temperature/lower-density gas.

The computational results shown here were performed over a single core.For sustained flight, it is anticipated that cores will be createdrepetitively. Different repetition rates will result in different energyefficiencies. The general trends of the numerical data suggest greaterdrag reduction for larger core diameters. Also, although there areexceptions, greater return on invested energy appears to generally beobtained at higher Mach numbers and for less stream-lined bodies (largerhalf-angle cones).

Example 1

FIGS. 1 1A-D illustrate use of the invention with a body 101 moving tothe right through a fluid 105 at supersonic speed. In FIG. 1 A, the body101 is moving to the right through the fluid 105 at supersonic speed, asindicated by a shock wave 103 ahead of the body 101. In the rest frameof the shock wave 103, or equivalently the rest frame of the body 101,the fluid 105 ahead of the shock wave is moving to the left.

The invention is not limited as to a particular body 101. For example,the body 101 could be an airplane, a missile, a launch vehicle, aprojectile, a re-entry vehicle, or any subsystem or protrusion thereon,such as an engine, the body's nose, an external fuel tank, a fairing, atail, a wing, or external instrumentation. Furthermore, the invention isnot limited as to the particular fluid 105 through which the body 101passes. Additionally, the fluid flow need only be locally supersonic toyield a shock wave 103. The body 101 also includes a port 102 throughwhich energy is directed. Examples of ports are described in more detailwith regard to FIG. 15.

In FIG. 11B, an energy beam 104 is emitted from the port 102 and travelsoutward typically at the speed of light. This energy beam 104, ascompared to the time scale of the fluid flow, suddenly heats an extendedpath of the fluid 105 ahead of the body 101. In this particular example,the energy is electromagnetic in nature, and results from the use of alaser pulse which can be, but is not limited to, an ultra-short laserpulse in the ultraviolet to the infrared range. The result of thisheating method is the long, hot, ionized filament in fluid 105 along thepath of the energy beam 104.

In FIG. 11C, the hot filament expands over a heated core 160, whichweakens the shock wave 103 and can even temporarily locally eliminatethe shock wave 103. As the body 101 travels into the expanding or fullyexpanded heated core 160, the shock wave 103 is locally eliminated whenthe speed of the body 101 is less than the local speed of sound withinthe heated core 160. Fluid 105 is most effectively moved out of the wayof the body 101, when the heated core 160 is parallel to the directionof the body's movement through the fluid 105. This results in the mosteffective drag reduction and sonic boom mitigation in the acoustic farfield of the body 101.

In FIG. 11D, the shock wave 103 is re-established once the effect of theheated core 160 is no longer experienced by the shock wave 103. Althoughthe heated core 160 can extend over hundreds of meters or more, theheated core 160 cannot extend infinitely. Therefore, the effect of theheated core 160 on the shock wave 103 not only diminishes, as the heatedcore expands outward, but also disappears once the end of the hot coreis reached.

Example 2

FIG. 12 illustrates a use of the invention with a body 101 that ispassing through a fluid 105 with a non-zero angle of attack A. The body101 includes an energy discharge device 102 that creates a heated corealong an extended path 108 through a shock wave 103 in front of the body101. Although the extended path 108 is parallel to the motion of thebody 101 through the fluid 105, the angle of the extended path 108 fromenergy discharge device 102 is not parallel to the body center axis(BCA) of the body 101 because of the non-zero angle of attack A of thebody 101. In fact, the preferential drag reduction resulting from theoff-center/asymmetric application of the heating can be used topartially or fully maintain the non-zero angle of attack A, in additionto reducing the overall drag on the body 101.

Example 3

A method of increasing the energy deposition along a heated path throughthe use of electric discharge is illustrated in FIG. 13. A body 101passing through a fluid 105 at supersonic speed such that a set of shockwaves 103 is created adjacent to the body 101. The body includes threeenergy emitting mechanisms 106, 107. Although illustrated having twoside energy emitting mechanisms 106 and a single central energy emittingmechanism 107, the invention is not limited in this manner. Each energyemitting mechanism 106, 107 can include one or more separate energyemitting mechanisms, and if multiple mechanism are used, these multiplemechanism can be linked in an array and/or be separate from one another.

Two of the energy emitting mechanisms 106 can be charged with a givenpolarity, and a third energy emitting mechanism 107 can be oppositelycharged. Alternatively, the center energy emitting mechanism 107 canhave an intermediate voltage relative to the two side energy emittingmechanisms 106. For example, the center energy emitting mechanism 107can have a higher voltage than the energy emitting mechanism 106 on theright wing and a lower voltage than the energy emitting mechanism 106 onthe left wing. Alternatively, the central potential of the energyemitting mechanism 107 can be at ground, the left energy emittingmechanism 106 can be positive, and the right energy emitting mechanism106 can be negative. An example of an energy emitting mechanism isexplained in more detail with regard to FIG. 14.

As used herein, the term “ground” refers to the average potential of thebody 101, and the term “oppositely charged” refers to the relationshipbetween one potential, which is greater than “ground,” and anotherpotential, which is below “ground.” Thus, as discussed above, adischarge between two locations, such as nose and wings of the body 101,can be achieved by having the nose at a different potential from thewings, which are maintained at a common potential. A conducting path isthen created between wings and nose to generate the desired electricdischarge, which deposits energy into the flow. The wings do not have toshare a common potential to generate the desired discharges. Forexample, one wing may have an electric potential above the electricalpotential of the nose, while the other wing may have an electricalpotential below the electrical potential of the nose. This can helpensure that discharge will take place simultaneously between the noseand both wings instead of discharging only between the nose and onewing).

It should be noted that any suitably large difference in electricpotentials can be used to generate an electric discharge between twoelements without regard to potentials of other elements, or the timingof independent discharges. Thus, discharges between elements can beimplemented given a sufficient voltage difference between the elementsin question and given suitable nucleation of the discharge. Thisimplementation is independent of the electrical potential of otherelements and the timing of other discharges.

To better control the electric discharge path of the energy emittingmechanisms 106, 107, each of the energy emitting mechanisms includes anelectromagnetic discharge port that is capable of ionizing a path 108through the fluid 105. The conductive ionized paths 108 intersect at apoint PI ahead of the body 101 and ahead of the shock wave 103. Theionized paths 108 provide a conductive circuit along which theoppositely charged energy emitting mechanisms 106, 107 can discharge.Such an electric discharge can deposit energy into the fluid 105 moreeconomically than with electromagnetic radiation alone.

The geometry shown creates a heated core along the ionized paths 108 a,108 b. As such, not only is fluid heated immediately in front of thebody 101 along the stagnation line on the axis of symmetry using oneionized path 108 b, but the heated cores along ionized paths 108 a canalso have the ancillary benefit of pushing some fluid 105 out of the wayof the wings of the body 101. However, because these ionization paths108 a are not along incoming streamlines, the effect of the heated coresis not as efficient, nor as effective as the heated core along thecenter ionized path 108 b. This example with the stagnation line beingcollinear with an axis of symmetry is illustrative, and is not meant tobe restrictive.

As previously discussed, microwave energy can be used in addition to, orin place of, the electric discharge to create the heated core. Thus,instead of emitting an electric discharge to heat the ionized path, theenergy emitting mechanisms 106, 107 can include microwave emitters.Although three microwave emitters 106, 107 are illustrated in FIG. 13, asingle microwave emitter can be used or several microwave emitters canbe used. Furthermore, instead of having the energy emitting mechanisms106, 107 be microwave emitters, the one or more microwave emitters canbe in addition to the energy emitting mechanisms 106, 107 that emit theelectric discharge, filamenting laser, and/or other energy. It should befurther noted that the invention is not limited to microwaves and/orelectric discharge being emitted from the energy emitting mechanisms106, 107, as other types of energy can be emitted.

A more specific manifestation of the energy emitting mechanismspreviously discussed in FIG. 13 is illustrated in more detail in FIG.14. A body 101 includes several directed energy ports 106, 107. Theenergy ports 106, 107 are electrically isolated from each other, withtwo of the energy ports 106 having one polarity and the other energyport 107 having an opposite polarity. The electric discharge from theenergy ports 106, 107 can be driven by one or more charge-storage and/orvoltage-supply elements 114.

The electromagnetic energy is emitted from a source 110, which canconsist of a single emitter, as illustrated, or several emitters. Theelectromagnetic pulses 111 can be generated in rapid enough successionto be considered effectively instantaneous by the fluid dynamics beingcontrolled. Additionally, if only one emitter is used, a single pulse111 a may also be split at a splitter 112 and sent to the differentelectromagnetic emission ports 102. The split pulses 111 b can beredirected using reflecting elements 113 and sent through focusingelements at the emission ports 102 to create the desired conductingcircuit of ionized paths 108 to initiate and guide the electricdischarge from the energy ports 106, 107.

The entire process can be continually monitored by environmental sensors115 to ensure effective implementation of the process through continualadjustments to the electric and electromagnetic discharges toaccommodate changing factors and needs. The electrical isolation of theenergy ports 106, 107 is aided because only optical coupling is requiredin the internal systems. An example of an optical system for use withthe emission ports 102 is described in more detail with reference toFIG. 15.

A more specific manifestation of an emission port previously discussedin FIG. 14 is illustrated in more detail in FIG. 15. If necessary,reflecting elements 113 direct the pulse 111 of electromagnetic energyinto the emission port 102. The emission port 102 includes focusingelements 121 that are adjustable with a mechanism 122 to control thepoint at which the ionized path begins. Additionally, an electricallyconducting tapered housing 123 can be included with the emission port102 to couple an electric discharge to the ionized path created by theelectromagnetic pulse 111.

Example 4

An array of energy discharge devices is illustrated in FIGS. 16A, 16B.An array of energy emitting mechanisms or elements 106 a, 106 b, 106 cis arranged on a body 101. The body 101 includes a central element 106 asurrounded by an inner annular array of elements 106 b and an outerannular array of elements 106 c. The total array of elements 106 can beused to increase effectiveness of the invention by firing the individualelements 106 or groups of elements 106 in succession. The effectivenessof the invention can be increased by using the array of elements 106 tocontinue to push the fluid 105 cylindrically outward, after the fluidexpanded outward from the central heated core, generated by the centralelement 106 a.

Although the elements 106 shown emit an electrical discharge, the arrayis not limited in this manner. For example, the array can include bothelectric discharge elements 106 and electromagnetic emission ports orcan consist of only electromagnetic emission ports. In this example,when an electrical discharge is being used, the electrical dischargefollows ionized paths 108 that complete separate conducting circuitsbetween elements 106 b and 106 a. The next set of conductive paths anddischarges could then be between 106 c and 106 a (or 106 b).

In operation, as illustrated in FIG. 16A, the central element 106 a andone or more elements 106 b of the inner array would be fired to create acentral heated core 160 a. This heated core would expand outward,possibly bounded by a cylindrical shock wave, which would weaken withthe expansion. To add energy to the weakened cylindrical expansion,elements 106 b could be fired, as illustrated in FIG. 16B. Upon furtherexpansion, elements 106 c of the outer array would then also be fired tomaintain a strong continued expansion of the heated core 160 b.

Example 5

Use of the method of the present invention with a propulsion unit, suchas a scramjet 130, is illustrated in FIG. 17. When fluid 105, such asair, enters the scramjet 130 at a sufficiently high velocity, a shockwave 103 develops within the scramjet 130. By positioning energydischarge device(s) 102 and possibly thin electrodes 180, whetherelectric discharge, electromagnetic, or both, within the intake of thescramjet 130, a heated core expanding from the path of energy deposition108 can be created within the scramjet to “puncture” the shock wave 103according to the invention. In addition to mitigating efficiency lossesdue to the shock wave, the heated core can also provide the ancillarybenefits of heating and ionizing the fluid to help the reaction in thescramjet engine, as well as helping the mixing process and energyrecuperation.

Although shown positioned in the flow path of the scramjet 130, theenergy discharge device(s) 102 are not limited to these particularpositions. The energy discharge device(s) 102 can be located in anypositions that advantageously allow the energy discharge device tomodify a shock wave according to the invention. For example, the shockwave can be located in front of the intake; and therefore, the energydischarge devices can also be located in front of the intake, ifnecessary. Furthermore, this concept can be applied to similar types ofgeometries, including the inlets and flow paths of other types ofpropulsion units.

Example 6

The use of the invention with supersonic spray deposition is illustratedin FIG. 18. In this process, particles are propelled at supersonic speedthrough a nozzle 140 toward a target 142. One or more shock waves 103can develop in various positions within and outside of the nozzle 140.One of the problems caused by the shock waves 103 in this process is thesegregation of particle sizes and densities which occurs when crossingthe shock wave 103. An energy discharge device 102 can be placed withinthe nozzle 140 to create a heated core along a streamline ahead of theshock wave 103. The energy discharge device can use directed ionizingelectromagnetic radiation alone, or use this ionization to initiate andguide an electric discharge.

As the target 142 can be electrically conducting, the electricaldischarge path 108 can be much less complicated, potentially requiringonly one energy discharge device 102 to complete a circuit from theelectrical discharge. Additionally, the use of electric discharge ispossible without creating an ionized path to guide the electricdischarge. This can be accomplished by using particular electrodegeometries in conjunction with electrically insulating materials in thenozzle 140. In addition to mitigating the shock, both electromagneticradiation and electric discharge can advantageously modify depositionprocesses and surface treatments.

Example 7

One embodiment of the present invention to reduce noise is illustratedin FIG. 19. Shock waves and expansion waves 170 are formed in theexhaust 146 of a propulsion unit 148, such as a jet turbine,after-burner, rocket motor/engine, or other types of propulsion units.In such a situation, the shock and expansion waves 170 typically form“shock diamonds,” which can be established within the exhaust. Thesepatterns can contribute strongly to an augmentation of the acousticsignature in certain frequency ranges, which is sometimes referred to as“screech.” The method of the present invention can disrupt thesepatterns by providing a heated core along an extended path 108 throughthe pattern of expansion and shock waves 170. This technique can also beused to dissipate shock waves formed within the propulsion unit.

The heated core can be formed using electromagnetic radiation and/or anelectric discharge. In the situation of an electric discharge, the needto ionize the fluid so as to obtain a path for the electric discharge isnot necessary as the exhaust is already partially electricallyconductive, and erratic disruption is sufficient to disrupt thisparticular shock wave pattern. The existing ionization may also have adeleterious effect on the propagation of certain electromagneticfrequencies.

Example 8

A schematic representation of one possible application of a linear arrayof energy discharge devices 102, similar to those depicted in FIGS. 14and 15, is illustrated in FIG. 20. The energy discharge devices 102 aremounted on a vehicle 101 to push incoming fluid 105 outward along thewing 150, in a wavelike motion, by firing sequentially from theinnermost energy discharge device 102 a to the outermost energydischarge device 102 f furthest from the centerline of the vehicle 101.These energy discharge devices 102 can either be limited to ionizingelectromagnetic radiation, or coupled with electrical discharge units.

The energy discharge devices 102 would typically be electricallyisolated, as with the connecting charging units and switches.Additionally, neighboring energy discharge devices can be firedeffectively simultaneously to create an electrically conducting path108, as previously discussed with regard to FIGS. 13 and 14. The energydischarge devices 102 can also be fired successively in pairs to use theelectric discharges to sweep the fluid 105 outward toward the tips ofthe wing 150. Either with or without electric discharge, this method ofsweeping fluid toward the wingtips also directs the fluid over and underthe wing 150. Environmental sensors can also be included to monitorperformance and be coupled to the energy discharge devices to modify thedifferent parameters of the energy deposition.

Example 9

Application of the method of the present invention to a submersible body101 is illustrated in FIGS. 21A, 21B. Energy is emitted from an energydischarge device 102 located in the submersible body 101 along anextended path 108 in the liquid 105 ahead of the body 101. Theelectromagnetic coupling constants to dense fluid, such as liquid 105,are typically greater than those to gas, and the strongly heated liquid105 can also vaporize. This results in a channel 160 of gas developingfrom the heated liquid path 108 through which the body 101 can pass.This channel 160 of gas has a very low-density, compared to its liquid.As a result, even if the body 101 is not traveling supersonically, andthere is no shock wave, a significant decrease in drag on the body 101occurs. Additionally, the path 108 can be actively directed in differentdirections to asymmetrically change pressures exerted against the body101 to steer the body 101 through the liquid 105. The approach ofactively directing the heated path 108 to asymmetrically changepressures exerted against the body 101 to steer the body 101 can also beused when the body 101 is traveling through a gas, such as air.

Example 10

FIG. 22 illustrates use of the method of the present invention toprovide a heated core 160 from an energy discharge device 102 positionedin front of the shock wave 103 of a body 101. As shown, the energydischarge device 102 can be positioned at a location 152 remote from thebody 101. In this manner, the energy discharge device 102 dischargesenergy to create an extended heated core 160 in front of the body 101and/or the shock wave 103. The remote location 152 may be land-based,sea-based, or space-based, which may dictate the form of the energydeposition.

Example 11

FIG. 23 illustrates the use of an energy discharge device 102 to heatalong an extended path 108 ahead of a protrusion 154 on a body 101. Theprotrusion 152 on the body 101 can be a source of additional drag on thebody 101. As such, by using an energy discharge device 102 to heat alongan extended path 108 ahead of the protrusion 154, the drag due to theprotrusion 154 can be reduced. Additionally, the temperature andpressure at the protrusion 154 can be reduced through control ofsupersonic flow, a shock wave, or interacting shock waves.

Example 12

FIG. 24 illustrates the use of an energy discharge device 102 in apropulsion unit 148 to deposit energy along an extended path 108 withinthe propulsion unit 148. The creation of a heated core along theextended path can be used to puncture/disrupt any internal shock waves103, as well as resonances, that may be established within thepropulsion unit 148.

Example 13

FIGS. 25A-E illustrate some examples of the great variety of differentgeometries in which energy discharge devices 102 can be arranged on abody 101. The different geometries of energy discharge devices 102 canbe arranged to reduce drag on the body 101, maneuver the body 101,mitigate sonic boom, or control a shock wave and/or fluid flow, forexample by sweeping fluid in given directions, including cylindricallyor linearly outward. In addition, the application of a linear array ofenergy discharge devices 102 can be formed on the blades of a helicopterrotor to reduce the helicopter's acoustic signature.

Example 14

FIG. 26 illustrates the use of the present invention to form a heatedcore in front of a light craft 101 without the need of providing anenergy discharge device on the craft 101. In operation, a beam 162 ofelectromagnetic energy is directed toward the craft 101. The craft 101includes focusing elements 163 that will further focus the beam 162 toheat the fluid 105 in front of the craft 101 along an extended path 108.The path 108 can be in the form of a line of heated/ionized gasresulting from a “filamenting” laser pulse, as previously discussed.

Such a concept would allow the craft 101 to take advantage of the shockwave/flow control and drag reduction provided by use of the inventionwithout having to carry the energy generation equipment. Such a conceptcan also be used with an additional directed electromagnetic energy unitused to provide propulsion for the light craft 101 of the type known tothose familiar with the art. Such a system could be used as aninexpensive launch vehicle from a planet with an atmosphere.

Example 15

FIGS. 27A, 27B and 27C illustrate the use of the present invention toform a volume of low-density, heated fluid, hereinafter referred to ascore 160, in a fluid 105 through which a body 101 will pass. The body101 can contain a shroud encompassing one or more symmetrical inlets 190that surround the body 101. FIG. 28 illustrates an alternativeembodiment using the same technique in which the body 101 includes oneor more non-symmetrical inlets 190. In FIG. 27A, an energy dischargedevice 102 positioned on the body 101 heats gas, such as air, along anextended path 108 from the body 101. The energy discharge device 102 canalso be adjusted to change the orientation of the extended path 108relative to an orientation of the body 101.

Although not limited in this manner, the body 101 includes a propulsionsystem 195, such as a scramjet engine. Although not limited in thismanner, the cowling 197 directs a shockwave (not shown) directly intothe inlet 190 to be used in the propulsion system 195. An example ofsuch a device would be a projectile, which may or may not begun-launched. One disadvantage of a class of prior scramjet-poweredprojectiles is that they can only work at very high altitudes, such as80,000 ft., since air is too dense, for example, near sea level. Thereason for this is at least two-fold. A high density atmosphere createssignificant friction and heating, which wears the projectile down beforeit can travel the desired distance. In addition, the amount of airentering the scramjet may be too great to be properly handled by thepropulsion system 195. As the projectile is preferably gun-launched,such a projectile previously could not be practically implementedbecause of the impracticalities of gun-launching the projectile at highaltitudes.

The present invention, however, is capable of overcoming the problemsassociated with a high density atmosphere by decreasing the density ofthe air in front of the projectile, thereby allowing the projectile tobe launched from conventional ground- or sea-based systems in additionto air-based systems. In the same manner, the extent to which thedensity is decreased can also be changed by varying the temperature andthe size of the core 160. This enables tailoring of an exact amount ofair to be provided to the propulsion system 195. For example, in FIG.27C, the low-density core 160 can push most of the air 105 completelyout of reach of the intake 190, or as shown in FIG. 27B, the low-densitycore 160 can provide a considerable amount of the air 105 to the inlet190. Alternatively, the low-density core 160 can allow some intermediateamount of air 105 to enter the inlets 190 (not shown).

The present invention can be practiced by employing conventionalmaterials, methodology and equipment. Accordingly, the details of suchmaterials, equipment and methodology are not set forth herein in detail.In the previous descriptions, numerous specific details are set forth,such as specific electromagnetic pulse details, materials, structures,chemicals, processes, etc., in order to provide a thorough understandingof the present invention. However, it should be recognized that thepresent invention can be practiced without resorting to the detailsspecifically set forth. In other instances, well known processingstructures have not been described in detail, in order not tounnecessarily obscure the present invention.

Only an exemplary aspect of the present invention and but a few examplesof its versatility are shown and described in the present disclosure. Itis to be understood that the present invention is capable of use invarious other combinations and environments and is capable of changes ormodifications within the scope of the inventive concept as expressedherein.

1-52. (canceled)
 53. A method of controlling flow of a first fluidthrough a second fluid comprising the steps of: creating an extendedpath of decreased density within a second fluid substantially parallelto the direction of flow of the first fluid within the second fluid byemitting energy at at least one point within a second fluid, andenabling the first fluid to flow through the extended path of decreaseddensity.
 54. The method of claim 53, wherein the at least one pointcomprising a plurality of points.
 55. The method of claim 53, whereinthe emitting energy is laser energy, electric discharge, microwavepulses, and/or some combination thereof.
 56. The method of claim 53,wherein the first fluid is gas, liquid, multi-phase fluid, or anair/fuel mixture.
 57. The method of claim 53, wherein the flow of thefirst fluid is subsonic, transonic, or supersonic.
 58. The method ofclaim 53, wherein the first fluid is able to flow within the secondfluid with increase range and/or speed.
 59. The method of claim 53,wherein the first fluid is able to flow within the second fluid withless energy.
 60. The method of claim 53, wherein the first fluid is ableto flow within the second fluid with decrease of undesired segregationof particles or particle size re-distribution.
 61. The method of claim53, wherein the first fluid is associated with a propulsion unit. 62.The method of claim 53, wherein the first fluid flows at least in partwithin a propulsion unit.
 63. The method of claim 62, wherein the effectis to control the air flow into the inlet of a propulsion unit.
 64. Themethod of claim 62, wherein the propulsion unit performance is enhanced.65. The method of claim 62, wherein the effect of a shock wave on thepropulsion unit is mitigated.
 66. The method of claim 62, wherein theeffect of a sonic boom on the propulsion unit is mitigated.
 67. Themethod of claim 62, wherein the any resonance and/or acoustic signaturethe propulsion unit is mitigated.
 68. The method of claim 62, whereinthe temperature of the propulsion unit is reduced.
 69. The method ofclaim 62, wherein the pressure of the propulsion unit is reduced. 70.The method of claim 53, wherein the flow of the first fluid iscontrolled.
 71. The method of claim 70, wherein the flow of the firstfluid is controlled into a propulsion unit.
 72. The method of claim 71,wherein the performance of the propulsion unit is enhanced.